今天整理以前一個項目源碼，發現兩個隨機生成不重復字符串的方法，覺得用起來挺方便的，在此貼出來，方便以后查閱。 

方法一：隨機生成不重復數字字符串 

復制代碼代碼如下:

private int rep=0; 

/// <summary> 
/// 生成隨機數字字符串 
/// </summary> 
/// <param name="codeCount">待生成的位數</param> 
/// <returns>生成的數字字符串</returns> 
private string GenerateCheckCodeNum(int codeCount) 
{ 
string str = string.Empty; 
long num2 = DateTime.Now.Ticks + this.rep; 
this.rep++; 
Random random = new Random(((int)(((ulong)num2) & 0xffffffffL)) | ((int)(num2 >> this.rep))); 
for (int i = 0; i < codeCount; i++) 
{ 
int num = random.Next(); 
str = str + ((char)(0x30 + ((ushort)(num % 10)))).ToString(); 
} 
return str; 
} 

方法二：隨機生成字符串（數字和字母混和） 

/// <summary> 
/// 生成隨機字母字符串(數字字母混和) 
/// </summary> 
/// <param name="codeCount">待生成的位數</param> 
/// <returns>生成的字母字符串</returns> 
private string GenerateCheckCode(int codeCount) 
{ 
string str = string.Empty; 
long num2 = DateTime.Now.Ticks + this.rep; 
this.rep++; 
Random random = new Random(((int)(((ulong)num2) & 0xffffffffL)) | ((int)(num2 >> this.rep))); 
for (int i = 0; i < codeCount; i++) 
{ 
char ch; 
int num = random.Next(); 
if ((num % 2) == 0) 
{ 
ch = (char)(0x30 + ((ushort)(num % 10))); 
} 
else 
{ 
ch = (char)(0x41 + ((ushort)(num % 0x1a))); 
} 
str = str + ch.ToString(); 
} 
return str; 
}